Hi everyone, I’m struggling with the same thing!
I’m no expert and I probably misunderstand because I’m not very familiar with Squarespace yet, BUT:
I see that there’s an option “Check out on your domain” which means you get redirected to a website to finish checkout, instead of Squarspace (right?). Paul already mentioned redirecting to Shopify, which is honestly a great idea, but can’t you also redirect to plugandpay (which has an option for ideal)? So the checkout takes place there? Or maybe there’s other websites which can be used for checkout and are bit cheaper than Shopify too..?
Apologies if I’m forgetting/misunderstanding something, I’m just really eager to find a solution :))